diff --git a/sklearn/decomposition/_pca.py b/sklearn/decomposition/_pca.py
index ac4a1d1d9816b..eb0a73919021a 100644
--- a/sklearn/decomposition/_pca.py
+++ b/sklearn/decomposition/_pca.py
@@ -217,6 +217,7 @@ class PCA(_BasePCA):
 
     explained_variance_ : ndarray of shape (n_components,)
         The amount of variance explained by each of the selected components.
+        The variance estimation uses `n_samples - 1` degrees of freedom.
 
         Equal to n_components largest eigenvalues
         of the covariance matrix of X.